Question

Two narrow slits are illuminated by a laser with a wavelength of 587 nm. The interference pattern on a screen located x = 5.00 m away shows that the second-order bright fringe is located y = 9.30 cm away from the central bright fringe.

A.) Calculate the distance between the two slits.

B.) The screen is now moved 2.5 m further away. What is the new distance between the central and the second-order bright fringe?

Answer 1

In interfreence or diffraction pattern

the needed equation is Y = mLR/d---------------1

and d sin theta = mL--------------------2

where L = wavelgnth

m = order = 1,2,3,4, ......... for brigth bands

m = 1.5, 2.5, 3.5, 4.5, ......for dark bands

R is the distance from slit to screen

Y = disatnce from central spot to nth order fringe or fringe width

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so here we apply d = mLR/Y

d = 2* 587 nm * 5/(0.093)

d = 0.063 mm

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here when R = 5+2.5 = 7.5 m

Y = 2* 587nm * 7.5/0.063mm

Y = 0.139 m